The present invention relates to a method and an apparatus for radially expanding or enlarging rings, in particular by means of rolling tools.
Methods of this general kind, in which ring blanks of steel or similar materials are rolled until the desired ring diameters and widths are attained, are known in the art.
Apparatuses are also known in which the ring blank rests with its inner radial surface on a rolling mandrel and with one end face on a rolling table. To center and hold the ring blank, rollers disposed on movable arms are pressed laterally against the outer annular face. A further roller, which is the main roller, presses against the outer radial surface of the ring blank opposite the rolling mandrel. When the apparatus is in operation, the ring travels between the main roller and the rolling mandrel so as to be rolled to the desired diameter. As a result of the rolling of the radial surfaces, however, the end faces are drawn concavely inward, resulting in a fish-mouth shaped deformation. The fish-mouth deformation is then removed later, on a second machine.
In order to overcome the disadvantage of fish-mouth deformation without using a second machine, apparatuses are used which have one pair of tools that machines the radial surfaces and another pair of tools that simultaneously rolls the end faces.
Such machines are very expensive, however, because they have two differently embodied pairs of tools which must each be controlled.